Bio-oxidation of arsenopyrite

Oxidation of arsenopyrite with Acidithiobacillus ferrooxidans was studied. The electrochemical results show that arsenopyrite is firstly oxidized to AS(2)S(2) at the potential of 0.2-0.3 V (vs SHE) and As(2)S(2) covers the electrode and retards the process continuously. While at higher potential over 0.3 V (vs SHE), As(2)S(2) is oxidized to H(3)AsO(3), and H(3)AsO(3) is then oxidized to H(3)AsO(4) at 0.8 V (vs SHE). The leaching results show that the addition of FeS(2) can promote the oxidation of As(3+) to As(5+) and increase the activity of the bacteria. The best bio-oxidation technical parameters are the initial pH of 1.8-2.0, particle sizes less than 0.074 mm, temperature in the range of 25-30 degrees C and rotating speed of the orbital incubator of 100-160 r/min. The results provide theoretical and technological supports of bio-oxidation arsenopyrite for pretreating refractory arsenic gold ores.